1. Field of the Invention
The present invention generally relates to cable handling and, more particularly, is concerned with an apparatus and vehicle for laying seismic line cable on the ground, for retrieving the laid cable from near the ground surface, and for transporting the cable over land.
2. Description of the Prior Art
Seismic exploration for oil and gas reservoirs underlying land areas often requires the laying and later retrieval of very long lengths of seismic line cable. Geophone sensors and electronic modules are usually attached at intermittent points along the length of the cable. The components, once deployed and connected together, form a long line, or lines, of seismic sensors, with attached remote electronic monitoring packages, and a system of interconnecting cables that carry each sensors"" output signals back to a seismic recording system. This attached sensitive electronic equipment requires that the seismic line cable be laid carefully. To obtain accurate seismic data, the geophone sensors attached to the cable must be placed or deployed on the ground surface in a vertical orientation, rather than tilted or sideways. When retrieving the seismic line cable from the ground after the exploration activities are completed, the cable must be held in tension to prevent the entangling of the sensors, electronic modules, and their lead wires with one another or with the seismic line cable.
Seismic exploration operations are often conducted in very harsh weather environments. For example, exploration activities in the Arctic are often performed at temperatures as low as minus 50xc2x0 C. The seismic line cable becomes stiff and inflexible at such low temperatures, which makes deploying cable at such temperatures difficult.
Present methods for transporting, deploying and later retrieving, and securing for further transport, the electronics, the wired arrays of seismic sensors, and the associated seismic line cables, are manual and time consuming. The common method for transporting and deploying these items is to transport the cables piled into a basket or bin mounted on a transport vehicle. The individual packages of electronic monitoring devices are placed into small bins on the vehicle, and the strings of sensors are grouped together by hanging the sensors, and associated interconnecting wire, by passing a rod through loops attached to the sensor""s interconnecting wire. The rod is often in the shape of a xe2x80x9csafety pin.xe2x80x9d The pin closes by latching one end into a clasp on the other end. The sensors are strung onto the pin, while it is open, until all the sensors, and their associated interconnecting wires, are secured by their attached loops onto the pin. The pin is then closed. The now full pin is hung onto the vehicle from hangers attached along the sides of the transport vehicle.
During the deployment process, the appropriate number of sensor arrays on pins, electronic module packages, and interconnecting cables are dropped off the vehicle at appropriate intervals along the line. Seismic exploration crew personnel walk along behind the vehicle and position the electronic module packages, stretch out the cables between the electronic modules, unpin the array of sensors and stretch them out along side the interconnecting cable. Each sensor is then installed into the ground. The end of the wired sensor array is terminated with an electrical connector that is then connected into the electronic package.
When the recording process is complete, the crew personnel again walk along the line picking up the sensors, grouping them again back onto the pins by sliding the end of the pin through the individual loops on the sensor""s wire. The seismic cable is then rolled up. All of these items are then placed back onto the vehicle to be transported to the next layout location. Hence, the present method for laying and retrieving seismic cable is slow and highly labor intensive.
Consequently, a need exists for an automated cable handling and transport apparatus and vehicle that is capable of both deploying and retrieving seismic cable having sensors and electronic modules attached intermittently along its length. Preferably, the apparatus and vehicle that meets this need can accomplish both deployment and retrieval of the cable without the constant need for personnel on the ground to assist in either action. In addition, the apparatus and vehicle will preferably be capable of maintaining a controlled amount of tension on the cable as it is being retrieved so as to prevent entangling of the cable components. Further, the apparatus and vehicle will preferably provide a means for energizing and testing the cable and its electronic components while the cable is being laid, so that mislaid or defective components can be relaid or repaired while personnel are still in their vicinity. Ideally, such an apparatus and vehicle will also provide a means for maintaining the stored cable at a temperature at which it can be easily handled and deployed.
The present invention addresses the aforementioned needs by providing a mechanized cable laying, retrieval, and transport apparatus and vehicle. In one exemplary application, the seismic line cable includes geophone sensors and electronic modules that are interconnected by sensor interconnect lead wires.
A powered reel mounted on a vehicle is used to lay out, retrieve, and hold for transport these three components as a single unit. The result is faster deployment and retrieval of the equipment. Also, the number of personnel required to perform the lay out and retrieval process is reduced. The number of personnel exposed to stress and weather related injuries is also reduced. The present invention permits the required seismic crew personnel to ride on the vehicle for operating the controls of the power reel unit.
According to one aspect of the invention, an apparatus and vehicle is provided for retrieving a length of cable from near the ground surface and transporting the retrieved cable. The apparatus and vehicle comprises a vehicle capable of movement over land and at least one cable reel is supported by the vehicle for spooling the cable thereon as it is being retrieved from near the ground surface. Means is associated with the vehicle for tensioning the cable being retrieved.
According to another aspect of the invention, an apparatus and vehicle is provided for transporting and laying cable on the ground. The apparatus and vehicle comprises a vehicle capable of movement over land and at least one cable reel supported by the vehicle for unspooling the cable therefrom as it is being laid. Means may also be associated with the vehicle for forming a channel in the ground for laying the unspooled cable therein.
According to a third aspect of the invention, an apparatus and vehicle is provided for laying cable on the ground, for retrieving cable from near the ground surface, and for transporting the cable. The apparatus and vehicle comprises a vehicle capable of movement over land and at least one cable reel supported by the vehicle for unspooling the cable therefrom when laying cable, and for spooling the cable thereon when retrieving cable. Means may also be associated with the vehicle for forming a channel in the ground for laying the unspooled cable therein. A motor is attached to the cable reel for tensioning the cable and for rotating the reel to spool the cable thereon. An arm has a first end pivotally attached to the vehicle and a second end extending away from the vehicle. The arm is pivotally biased upward and away from the ground surface. A guide roller is rotatably attached to the second end of the arm. The cable being retrieved passes over the guide roller so that the pivotally biased arm assists in tensioning the cable being retrieved. At least one sheave is rotatably mounted on the arm. The cable being retrieved passes over the sheave for flexing the cable so as to break up and remove any foreign material adhering to the cable.